Calculate the number of atoms in each of the following:- 52 moles of Ar
- 52 u of He
- 52 g of He.
- 52 moles of Ar
- 52 u of He
- 52 g of He.
Solution and Explanation
(i) 1 mole of Ar = 6.022 × 1023 atoms of Ar
∴ 52 mol of Ar = 52 × 6.022 × 1023 atoms of Ar
= 3.131 × 1025 atoms of Ar
(ii) 1 atom of He = 4 u of He
Or,
4 u of He = 1 atom of He
1 u of He = \(\frac 14\) atom of He
52 u of He = \(\frac {52}{4}\) atom of He
= 13 atoms of He
(iii) 4 g of He = 6.022 × 1023 atoms of He
∴ 52 g of He = 6.022 × 1023 × \(\frac {52}{4}\) atoms of He
= 7.8286 × 1024 atoms of He
Top Questions on Laws of Chemical Combinations
- "A given compound always contains the same proportion of elements" is a statement of
- MHT CET - 2025
- Chemistry
- Laws of Chemical Combinations
- Which of the following pairs of compounds cannot demonstrate the law of multiple proportions?
- MHT CET - 2025
- Chemistry
- Laws of Chemical Combinations
- Which law is illustrated by compounds H$_2$O and H$_2$O$_2$ formed from two different elements, H and O?
- MHT CET - 2025
- Chemistry
- Laws of Chemical Combinations
- Among the following pairs of compounds, the one that does not illustrate the law of multiple proportions, is
- KEAM - 2022
- Chemistry
- Laws of Chemical Combinations
- \(PCl_5\) is well known, but \(NCl_5\) is not. Because,
- JEE Main - 2022
- Chemistry
- Laws of Chemical Combinations
Questions Asked in CBSE Class XI exam
- Identify the substance oxidised, reduced, oxidising agent and reducing agent for each of the following reactions:
- \(2AgBr (s) + C_6H_6O_2(aq) \rightarrow 2Ag(s) + 2HBr (aq) + C_6H_4O_2(aq)\)
- \(HCHO(l) + 2[Ag (NH_3)_2] ^+ (aq) + 3OH^ - (aq) \rightarrow 2Ag(s) + HCOO ^- (aq) + 4NH_3(aq) + 2H_2O(l)\)
- \(HCHO (l) + 2Cu^{ 2+}(aq) + 5 OH^ - (aq) \rightarrow Cu_2O(s) + HCOO ^- (aq) + 3H_2O(l)\)
- \(N_2H_4(l) + 2H_2O_2(l) \rightarrow N_2(g) + 4H_2O(l)\)
- \(Pb(s) + PbO_2(s) + 2H_2SO_4(aq) \rightarrow 2PbSO_4(s) + 2H_2O(l)\)
- CBSE Class XI
- Oxidation Number
Figure 8.9 shows the strain-stress curve for a given material. What are (a) Young’s modulus and (b) approximate yield strength for this material?
- CBSE Class XI
- Stress-strain curve
- Arrange the bonds in order of increasing ionic character in the molecules: LiF, K2O, N2, SO2 and ClF3.
- CBSE Class XI
- Molecular Orbital Theory
- Three reasons why the author’s grandmother was disturbed when he started going to the city school.
- CBSE Class XI
- The Portrait of a lady
Two identical ball bearings in contact with each other and resting on a frictionless table are hit head-on by another ball bearing of the same mass moving initially with a speed V. If the collision is elastic, which of the following (Fig. 5.14) is a possible result after collision ?
- CBSE Class XI
- Collisions
Concepts Used:
Some Basic Concepts of Chemistry
Chemistry is a vast subject and for understanding its significance we can take help of following points:
- Chemistry plays an important role in understanding various subjects like physics, geology and biology.
- Chemistry is a core branch of science that explains us about the various compositional properties and interaction of matter. It also helps to understand various chemical reactions.
- Chemistry is important in order to understand the behaviour of fertilizers, alkenes, acids, salts, dyes, polymers, drugs, soaps and alloys in organic and inorganic chemistry.
- Chemistry plays an important role in various fields like healthcare, industrial, research, food, and farm activities.
Read More: Some Basic Concepts of Chemistry
Classification of Matter
There are two ways of classifying the matter:
(A) Physical Classification:
Matter can exist in three physical states:
- Solids - have definite volume and definite shape
- Liquids - have definite volume but not definite shape.
- Gases - have neither definite volume nor definite shape.
(B) Chemical Classification:
Based upon the composition, matter can be divided into two main types:
- Pure Substances are defined as a single substance (or matter) which cannot be separated by simple physical methods. Pure substances can be further classified as (i) Elements (ii) Compounds
- Mixtures are the combination of two or more elements or compounds which are not chemically combined together and may also be present in any proportion.